Delphi 的内存操作函数(4): 清空与填充内存

FillMemory、ZeroMemory 一目了然的两个函数, 但其实它们都是调用了 FillChar;

清空不过就是填充空字符(#0: 编号为 0 的字符), 说来说去是一回事.

为了下面的测试, 先写一个以十六进制方式查看内存的函数:

function GetMemBytes(var X; size: Integer):
string;

var

pb: PByte;

i: Integer;

begin

pb := PByte(X);

for i :=
0 to size -
1 do

begin

Result := Result + IntToHex(pb^, 2) +
#32;

Inc(pb);

end;

end;
{GetMemBytes end}

//测试:

var

p1: PAnsiChar;

p2: PWideChar;

s1: AnsiString;

s2: UnicodeString;

begin

p1 := 'ABCD';

p2 := 'ABCD';

s1 := 'ABCD';

s2 := 'ABCD';

ShowMessage(GetMemBytes(p1,4));
{41 42 43 44}

ShowMessage(GetMemBytes(p2,8));
{41 00 42 00 43 00 44 00}

ShowMessage(GetMemBytes(s1,4));
{41 42 43 44}

ShowMessage(GetMemBytes(s2,8));
{41 00 42 00 43 00 44 00}

end;

测试 FillMemory、ZeroMemory、FillChar 三个填充函数:

const

num = 10;

var

p: PChar;

begin

p := StrAlloc(num);

ShowMessage(GetMemBytes(p, num)); {从结果看出 StrAlloc 没有初始化内存}

FillMemory(p, num, Byte('A'));

ShowMessage(GetMemBytes(p, num)); {41 41 41 41 41 41 41 41 41 41}

ZeroMemory(p, num);

ShowMessage(GetMemBytes(p, num)); {00 00 00 00 00 00 00 00 00 00}

FillChar(p^, num, 'B');

ShowMessage(GetMemBytes(p, num)); {42 42 42 42 42 42 42 42 42 42}

StrDispose(p);

end;

此时, 我想到一个问题:

GetMem 和 GetMemory 没有初始化内存; AllocMem 会初始化内存为空, 那么

ReallocMem、ReallocMemory 会不会初始化内存?

测试一下(结果是没有初始化):

{测试1}.

var

p: Pointer;

begin

p := GetMemory(3);

ShowMessage(GetMemBytes(p, 3));

ReallocMem(p, 10);

ShowMessage(GetMemBytes(p, 10));
{没有初始化}

FreeMemory(p);

end;

{测试2}

var

p: Pointer;

begin

p := AllocMem(3);

ShowMessage(GetMemBytes(p, 3));

ReallocMem(p, 10);

ShowMessage(GetMemBytes(p, 10));
{没有初始化}

FreeMemory(p);

end;

另外: FillMemory、ZeroMemory 的操作对象是指针, 而 FillChar 的操作对象则是实体.